This paper presents a structural modeling analysis of transmission towers with varied leg length combinations to examine the structural effects of unequal leg lengths. Power transmission towers in ...mountainous areas often use unequal leg lengths to accommodate the changing slope of the terrain. In this study, three types of 345 kV steel transmission towers with the D-type bracing system were considered as analytical examples to discuss the internal force distribution of the tower structure subjected to a load under a fully wired condition. Different tower structural types exhibit similar structural characteristics. The upper part of the force distribution of a tower structure is less affected by varied leg length configurations. The central parts affected by unequal leg lengths are the extension part and the tower leg component. Analytical results indicate the critical elements of tower structures with unequal leg lengths, which can serve as a valuable reference for disaster prevention and reduction. In this study, the primary elements of the towers were all under the permissible strength even with the leg length differences exceeding the current specifications. This implies that adjusting the regulation of leg length differences of a transmission tower with unequal leg lengths can serve as the basis for future research, highlighting the advantages of unequal leg length tower applications.
Mechanical factors play critical roles in mammalian development. Here, we report that colony-growing mouse embryonic stem cells (mESCs) generate significant tension on the colony surface through the ...contraction of a three-dimensional supracellular actomyosin cortex (3D-SAC). Disruption of the 3D-SAC, whose organization is dependent on the Rho/Rho-associated kinase (ROCK) signals and E-cadherin, results in mESC colony destruction. Reciprocally, compression force, which is generated by the 3D-SAC, promotes colony growth and expression of Nanog and Oct4 in mESCs and blastocyst development of mouse embryos. These findings suggest that autonomous cell forces regulate embryonic stem cells fate determination and provide insight regarding the biomechanical regulation of embryonic development.
Display omitted
•The surface tension of mESC colony is dynamically evolved during proliferation•A 3D supracellular actomyosin cortex assembles around the colony surface of mESCs•The compressive stress inside mESC colony facilitates pluripotency gene expression•The 3D supracellular actomyosin cortex contributes to blastocyst development
Cells in an embryonic stem cell colony synergistically generate compression force by dynamically assembled cytoskeleton to facilitate the maintenance of colony morphology and pluripotency gene expression.
One of the most important elements for animal transportation is the packaging that ensures the safety and health of the transit. During the transport of live small animals, such as day‐old chickens, ...the animals may only stay in the boxes for a very limited period, in this case, 48 h. Therefore, it is important to be able to model the strength behaviour of these boxes concerning packaging material requirements and sustainability. The aim of this study was to determine the short‐ and relatively long‐term strength of day‐old chicken packages to better estimate packaging design and to use these data to establish an analytical creep model with suitable parameters that adequately approximate the measured data. Two types of packages were tested, and two types of creep models were used to model the creep strain‐time graphs. The creep behaviour of the two samples was tested at four different uniaxial load cases, with consistent environmental conditions during the tests (23°C and 50% relative humidity RH). At the two highest loads, both samples failed before the 48‐h cycle, indicating a significant difference in box strength between short‐term and long‐term load tests. The secondary creep strain rate increases with the magnitude of the compressive load. When comparing the two creep models for both box types, the Power law provided the best accuracy at the 50% of box compression test (BCT) load case, while at the other three load cases, the Andrade law showed better predictions.
Live animal transport packaging materials must meet many parameters, to ensure that animals receive adequate air, light and temperature during transport. These can be provided by ventilation holes cut into the boxes, which also affect the strength of the packages. This paper presents the experimental results on the short‐term and long‐term strength of day‐old chicken packages to better estimate packaging design and to use these data to establish an analytical creep model.
This study aimed to mathematically characterize the ultimate compression tolerance (UCT) as a function of spinal joint posture, loading variation, and loading duration. One hundred and fourteen ...porcine cervical spinal units were tested. Spinal units were randomly assigned to subthreshold cyclic loading groups that differed by joint posture (neutral, flexed), peak loading variation (10%, 20%, 40%), and loading duration (1000, 3000, 5000 cycles). After the assigned conditioning test, UCT testing was performed. Force and actuator position were sampled at 100 Hz. A three-dimensional relationship between UCT, loading variation, and loading duration was most accurately characterized by a second order polynomial surface (R
2
= 0.644, RMSE = 1.246 kN). However, distinct UCT responses were observed for flexed and neutral postures. A single second-order polynomial most accurately characterized the UCT - loading duration relationship (R
2
= 0.905, RMSE = 0.718 kN) for flexed postures. For neutral joint postures, separate second-order polynomial equations were developed to characterize the UCT - loading duration relationship for each variation group (R
2
= 0.618-0.906, RMSE = 0.617 kN-0.746 kN). These findings suggest that UCT responses are influenced by joint posture and these data may be used to inform ergonomic tools for the assessment of low back injury risk during occupational lifting.
The finite element method is a widely used numerical method to analyze structures in virtual space. This method can be used in the packaging industry to determine the mechanical properties of ...corrugated boxes. This study aims to create and validate a numerical model to predict the compression force of corrugated cardboard boxes by considering the influence of different cutout configurations of sidewalls. The types of investigated boxes are the following: the width and height of the boxes are 300 mm in each case and the length dimension of the boxes varied from 200 mm to 600 mm with a 100 mm increment. The cutout rates were 0%, 4%, 16%, 36%, and 64% with respect to the total surface area of sidewalls of the boxes. For the finite element analysis, a homogenized linear elastic orthotropic material model with Hill plasticity was used. The results of linear regressions show very good estimations to the numerical and experimental box compression test (BCT) values in each tested box group. Therefore, the numerical model can give a good prediction for the BCT force values from 0% cutout to 64% cutout rates. The accuracy of the numerical model decreases a little when the cutout rates are high. Based on the results, this paper presents a numerical model that can be used in the packaging design to estimate the compression strength of corrugated cardboard boxes.
We aimed to investigate the association between breast compression and experienced pain during mammographic screening.
Using a questionnaire, we collected information on pain experienced during ...mammography from 1155 women screened in Akershus, February–March 2018, as a part of BreastScreen Norway. The questionnaire provided information on pain using a numeric rating scale (NRS, 0–10) and related factors. Data on compression force (Newton, N), pressure (kilopascal, kPa) and breast characteristics were extracted from the DICOM-header and a breast density software. Log-binomial regression was used to determine the relative risk (RR) of severe versus mild/moderate experienced pain associated with compression parameters, adjusting for breast characteristics and related factors.
Mean score of experienced pain was 2.2, whereas 6% of the women reported severe pain (≥7) during the examination. High body mass index (BMI) (≥27.3 kg/m2) was associated with a higher RR of pain scores ≥7 (RR 1.86, 95%CI 1.02–3.36) compared to medium BMI (23.7–27.2 kg/m2). Low compression pressure (4.0–10.2 kPa) was associated with a higher RR of severe pain (RR 2.93, 95%CI 1.39–6.20), compared with medium compression pressure (10.3–13.5 kPa) after adjusting for contact area, age, compressed breast thickness, volumetric breast density and BMI. The risk of severe versus mild/moderate pain (≥7 versus <7) decreased by 2% with increasing compression force (RR 0.98, 95%CI 0.97–1.00).
Women reported low levels of pain during mammography. Further knowledge about factors affecting experienced pain is needed to personalize the examination to the individual woman.
Pain in shoulder(s) and/or neck prior to screening should be considered by the radiographers in a practical screening setting. A compression force of 100–140 N and pressure of 10.3–13.5 kPa are acceptable with respect to reported pain during mammography.
Toll-like receptors (TLRs) represent a powerful system for the recognition and elimination of pathogen-associated molecular patterns (PAMPs) from bacteria, viruses, and other pathogens and ...damage-associated molecular patterns (DAMPs) released from dying cells. Typical PAMPs include bacterial cell wall components, viral pathogens, or pathogenic nucleic acids, including viral RNA and DNA. Activation of TLRs leads to the production of proinflammatory cytokines and type I interferons which are important for the induction of the host immune response against bacterial and viral infections. However, dysregulation and overstimulation can be detrimental, leading to hyper-inflammation, sepsis, and loss of tissue integrity. The involvement of TLRs in inflammation and bacterial infection has been recognized for a long time. There is an increasing number of reports demonstrating the involvement of TLR activation in a variety of viral infections, associated with protective immunity, but also immune hyper activation and even viral replication. Recent data show the involvement of TLR activation in various acute respiratory viral infections, including SARS-CoV-2 and indicate an essential role in COVID-19 pathology. It aimed to gather newest data and hypotheses regarding molecular and cellular mechanisms of TLR triggering and activation and their downstream signaling pathways by viral infections, and their correlation to immunology and pathophysiology of the associated diseases, to facilitate translational research resulting in new targets for the treatment of viral infectious diseases including COVID-19.
Insufficient interfragmentary compression force (IFCF) frequently leads to unstable fixation of osteoporotic lateral tibial plateau fractures (OLTPFs). A combined cancellous lag screw (CCLS) enhances ...IFCF; however, its effect on OLTPF fixation stability remains unclear. Therefore, we investigated the effect of CCLS on OLTPF stability using locking plate fixation (LPF).
Twelve synthetic osteoporotic tibial bones were used to simulate OLTPFs, which were fixed using LPF, LPF-AO cancellous lag screws (LPF-AOCLS), and LPF-CCLS. Subsequently, 10,000 cyclic loadings from 30 to 400 N were performed. The initial axial stiffness (IAS), maximal axial micromotion of the lateral fragment (MAM-LF) measured every 1000 cycles, and failure load after 10,000 cycles were tested. The same three fixations for OLTPF were simulated using finite element analysis (FEA). IFCFs of 0, 225, and 300 N were applied to the LPF, LPF-AOCLS, and LPF-CCLS, respectively, with a 1000-N axial compressive force. The MAM-LF, peak von Mises stress (VMS), peak equivalent elastic strain of the lateral fragment (EES-LF), and nodes of EES-LF > 2% (considered bone destruction) were calculated.
Biomechanical tests revealed the LPF-AOCLS and LPF-CCLS groups to be superior to the LPF group in terms of the IAS, MAM-LF, and failure load (all p < 0.05). FEA revealed that the MAM-LF, peak VMS, peak EES-LF, and nodes with EES-LF > 2% in the LPF were higher than those in the LPF-AOCLS and LPF-CCLS.
IFCF was shown to enhance the stability of OLTPFs using LPF. Considering overscrewing, CCLS is preferably recommended, although there were no significant differences between CCLS and AOCLS.
A two factor, three level (32) face centred, central composite design (CCD) was applied to investigate the main and interaction effects of tablet diameter and compression force (CF) on hardness, ...disintegration time (DT) and porosity of mannitol based orodispersible tablets (ODTs). Tablet diameters of 10, 13 and 15mm, and CF of 10, 15 and 20kN were studied. Results of multiple linear regression analysis show that both the tablet diameter and CF influence tablet characteristics. A negative value of regression coefficient for tablet diameter showed an inverse relationship with hardness and DT. A positive value of regression coefficient for CF indicated an increase in hardness and DT with increasing CF as a result of the decrease in tablet porosity. Interestingly, at the larger tablet diameter of 15mm, while hardness increased and porosity decreased with an increase in CF, the DT was resistant to change. The optimised combination was a tablet of 15mm diameter compressed at 15kN showing a rapid DT of 37.7s and high hardness of 71.4N. Using these parameters, ODTs containing ibuprofen showed no significant change in DT (ANOVA; p>0.05) irrespective of the hydrophobicity of the ibuprofen.
Summary
Recently, highly porous metal foams have been used to replace the traditional open‐flow channels to improve gas transport and distribution in the cells. Deformation of flow plate, gas ...diffusion layer (GDL), and metal foam may occur during assembling. When the cell size is small, the deformation may not be significant. For large area cells, the deformation may become significant to affect the cell performance. In this study, an assembling device that is capable of applying uniform clamping force is built to facilitate fuel cell assembling and alleviate the deformation. A compressing plate that is the same size of the active area is used to apply uniform clamping force before surrounding bolts are fastened. Therefore, bending of the flow plate and deformation of GDL and metal foam can be minimized. Effects of the clamping force on the microstructures of GDL and metal foam, various resistances, pressure drops, and cell performance are investigated. Distribution of the contact pressure between metal foam and GDL is measured by using pressure sensitive films. Field‐emission scanning electron microscope is used to observe the microstructures. Electrochemical impedance spectroscopy analysis is used measure resistances. The fuel cell performance is measured by using a fuel cell test system. For the cell design used in this study, the optimum clamping force is found to be 200 kgf. Using this optimum clamping force, the cell performance can be enhanced by 50%, as compared with that of the cell assembled without using clamping plates. With appropriate clamping force, the compression force distribution across the entire cell area can approach uniform. This enables uniform flow distribution and reduces mass transfer resistance. Good contact between GDL and metal foam also lowers the interface resistance. All these factors contribute to the enhanced cell performance.
An assembling device capable of applying uniform clamping force is built to facilitate fuel cell assembling and maintain the flow field uniformity.
With the optimum clamping force of 200 kgf, the cell performance is enhanced by 50%, due to reduced mass transfer resistance and interface resistance provided by the resultant uniform compression pressure distribution.
PDF
